Grading machine



April 14, 1925. 1,534,014;

/ c. E. GILLETT GRADING MACHINE Filed Oct. 22, 1919 2 Sheets-Sheet 1 W/T/VESS INVENTOR M7?%r 4 Gan/MM 6711a? April 14, 1925. 1 1,534,014

C. E. GILLETT GRADING MACHINE Filed Oct. 22, 1919 2 Sheets-Sheet 2INVENTOR W T/VES 5 flmisT 6/41- 577 Patented Apr. 14, 192 5.

UNITED STAT i t E. GILLETT, 0F "WORCESTER, MASSACHUSETTS, .ASSIGNOB, TO:NORTON COM- PANY, OF WORCESTER, MASSACHUSETTS, A CORPORATION OFMASSACHUSETTS.

GRADING MACHINE.

Application filed October 22, 1919. Serial No. 332,518.

To all whom it may concern:

Be it known that 1, CHARLES E. Gmnrr, acitizen of the United States ofAmerica, residing at Worcester, in the county of Worcester and State ofMassachusetts, have invented certain new and useful Improvements inGrading Machines, of which the following is a full, clear, and exactspecitalline alumina or silicon carbide granules 3 bonded by vitrifiedclay material, is to predetermine the cutting ability and other indingcharacteristics of the wheel when it is used in a grinding machine. Thisis usually donebyv testing a wheel which has proven satisfactory for acertain class of work with a grading machine which indicates certaincharacteristics under duplicate tests and comparing wheels to be gradedwith this standard. The :grade' of such wheels has heretofore beendetermined by a test of the hardness of the. clay bond and has notadettluately taken the physical char-1 acteristics o the abrasive graininto account, since a wheel made of weak, eas ly fractured abrasivegrains will have a diflerent grinding ability from one made of toughabrasive grains, although the clay bonds in the two wheelsmay be alike.

One object of my invention is to provide a simple and accurate method ofclassifying abrasivebodies and similar articles and to utilize a machinefor this purpose which may be easily used by an unskilled operator toobtain uniform results and a satisfactory classification of the bodybeing graded relative to a standard body.

' It is a further object to utilize for classifying such articles theprinciples involved in relatively moving the tool and the article beinggraded in frictional engagement along an extensive pathand measuring andcomparing the frictional forces involved.

To the accomplishment of these objects and such others as mayhereinafter appear, as will be readily understood by those skilled inthe art,'the invention comprises the general features and combination ofparts heremafter described and more particularly pointed out in theappended claims.

The preferred embodiment of the machine for carrying my improved methodof grading into practical effect is illustrated in the accompanyingdrawings in which Fig. 1 is a plan view of the machine, certain partsbeing omitted for the sake of clearness;

Fig. 2 is an elevation of the machine shown in Fig. 1; i

Fig. 3 is a plan of a modified form of the machine shown in Figs. 1 and2;

Figci 4 is'a section on the line 44 of Fig. 3; an

Fig. 5 is a section on the line 55 of Fig.

cation of the characteristics of the wheel, I

prefer to measure also the wear on the tool under standard conditionswhich taken with the measure of friction enable one to duplicate wheelswith a high degree of exactness and thus to accurately foretell theworking ability of the wheel as is indicated by the grade mark.

In accordance with the illustrated embodiment of my invention I classifysuch bodies as grinding wheels by determining the variation in the forcerequired to hold either the wheel or tool stationary while the otherpart is moved relatively thereto along what may be termed an extendedpath, which force varies in, accordance with the frictionalcharacteristic of the wheel, the tool of course being of the same sizeand material and exertin the same pressure on the wheel for all whee sbeingjcompared. In addition to determining the friction exerted by orupon a standard tool I also preferably measure the wear or abrasiveaction on the tool under standard conditions as a second indication ofthe cutting action of the wheel when in use. 0

Referring to Figs. 1 and 2, the wheel 10,

means of a clamping screw 17.

, rotating in the direction is mounted to turn in a suitable base 14which also supports a movable tool-carrying arm 15 in which a tool 16.is secured by The arm 15 is weighted if necessary, as b pi oduce thedesired pressure between the tool and the wheel and, in order that thetool as it is worn away may move toward the wheel, the arm 15 is mountedon a hinge member 19 pivotally mounted on the base 14 between ears 20.When the wheel is of the arrow shown in Fig. 1, the tool tends to movewith the wheel and I make use of this fact to determine the cuttingcharacteristics of the wheel which have a definite relation to the forcerequired to restrain the tool from movement under the frictional actionof the wheel when it is rotated. To this end the arm 15 is pivotallymounted on a vertical pivot 23 formed on the hinge member 19 so that itis capable of movement in a plane parallel to the plane of rotation ofthe wheel. This movement is restrained by a measuring instrument, suchas a dynamometer, which mdicates the force acting on the arm tending tocause it to move with the wheel. A convenient form of dynamomcter isillustrated in Figs. 1 and 2, which comprises a stud 24 passingthrough'a clearance hole 25 in the arm 15 and provided with a head 26,which engages one end of a helical spring 27 confined between it and thearm.

In order that the angular movement of the arm 15 under the influence ofthe wheelmay not vary the frictional effect, I provide means for movingthe arm to a radial position with respect to the Wheel inwhich positionit will receive the maximum frictional effect. For this purpose an arm28 is formed integral with the member 19 and is provided with aclearance hole for the stud 24. A

thumbnut 29 is provided on the stud so that the nut can be turned toexert a greater orless pressure on the arm 15 through the spring 27 sqas to bring the arm back to a radial position which will be indicated bythe position of apointer-BO with relation to an index mark 31 on the arm28. By this construction when the nut 29 is turned to bring the arm 15to a radial position as indicated by the pointer, the'force exerted bythe rotating wheel onthe arm will be indicated by the pointer 32 whichmoves over a scale 33 provided with any convenient graduation. In orderthat the starting friction,

or the friction of rest,'which will be greater than the correspondingforce required fter the parts have assumed their normal runningposition, may not be recorduring its Wear.

the weight 18 suspended therefrom, to

suitable source of power,

' iaseaomr ed, I prefer to observe the point at which the pointer 32comes to a substantially rest after the wheel has acquired its full orpredetermined speed. In order to observe a further abradingcharacteristic of the wheel I may utilize a wearable tool and providemeans for meas- For this purpose, I may provide a micrometer deviceindicated generally at 35, which may be conveniently mounted onanupright 36 formed integral with the base 14, so as tobe in position toreceive the tool 16 when it is swung into a vertical position about thehorizontal axis of the hinge member 19, as indicated in dotted lines inFig. 2. Since the wear will vary in accordance with the duration of thetest, it is essential that the test shall be conducted for a definiteperiod of time or that other means be employed for limiting the abrasiveaction of the wheel. In using the machine illustrated, the time oftreatment or the number of revolutions of the wheel is noted.

In the modification of the invention illustrated in Figs. 3, 4 and 5, asomewhat similar device is shown, the only essential distinction beingthat the grinding wheel shown in the modification remains stanow arywhile the tool moves, which is a reversal of the relative movement ofthese parts as shown in Figs. 1 and 2. As illustrated, the wheel 37is'non-rotatably held upon any convenient support, preferably in axialalignment with a vertical shaft 38 which is rotatably supported in themachine frame 39 and driven by the pulley 40. A radial arm 41 revolublymounted on the lower end of the shaft and held in place by the head 42is arranged to be turned by the shaft. This arm carries a wheel-engagingtool 43 which is vertically slidable through an aperture in the arm andis held down against the wheel 37 by a weight 44 guided in its Verticalmovement by two guide rods In order that the frictional resistance ofthe wheel acting to retard the movement of the tool may be observed, thetool is driven through a spring which forms, in eflect, a dynamometer.One arrangement for this purpose comprises a spring 46 having one endsecured to the shaft 38, as by a pin 47, and having the other endsecured to the arm 41 by means of a pin 48. The arm 41 is rotatablymounted on the lower end of the shaft 38 so that when the shaft isrotated, as by means of a pulley connected to any the arm 41 will bemoved through the agency of the spring 46, which will wind up more orless in accordance with the resistance to movement As it would beinconvenient to observe the angular, relation of the arm 41 and theshaft 38 during the rotation of the parts, I

detent 53 carried by the arm.

provide means for locking the parts in their relative position duringthe movement of the tool over the work. As it-is also found preferablenot to observe the starting force or the friction of rest which will befirst indicated by the movement of the spring, I also provide means forlocking thearm and shaft in their relative positions after the tool hasacquired its full speed, so as not to indicate the abnormal forceinvolved in starting the movement For this purpose, I have providedalockin device comprising a sleeve 49 slidably Ireye-d to the shaft 38andheld downwardly toward the arm 41 by a spring 50. The lower end ofthe sleeve 49 is provided with an enlarged flange 51 having a series ofteeth 52 any one of which is adapted to coop rate with a uring theinitial movement of the parts the. sleeve 49 is held in elevatedposition with the, detent 53 out of operative .relation with the teeth52 "by means of a book 54 mounted on any convenient fixed part of themachine frame 39. After the tool 43 has acquired its full speed thesleeve 49 maybe dropped by releasing the engagement of the hook54'so'that the detent 53 will engage one of the teeth 52 and lock thearm ll-with relation .to the shaft 38. i As illustrated in Fig. 5, theteeth 52 may be provided with any desired index numerals such asindicated at 55, so that the friction or resistance to movement offeredto the tool by various wheels may be compared by refegence to thesenumerals.

It will be obvious that. the modification of the invention illustratedin Figs. 3-and 4: maybe provided with a measuring device similar to thatshown in the preferred form of' the invention for measuring the wear onthe tool 43. As illustrated, however, the tool would .beremoved from thearm 41 and measured by any convenient instrument such as the usualhandmicrometer.

If it is desired to grade abrasive bodies by friction alone withoutconsidering tool wear, the tool may be of a relatively nonwearablematerial, such as a diamond, but. if the wear of-the tool is to bemeasured I prefer to use a tool of soft iron or steel not over A" indiameter on which the wear is large enough for convenient comparison. Myimproved method may. be carried'into practical effect by the machine'sillustrated, if it is so preferred, by adjusting the pressure on thetool until a standard power is indicated on the dynamometer and thendetermining this pressure due to the weight acting on the tool. In thiscase, the weights 18 (Figs. 1 and2) 6r 44 (Figs. 3 and 4) are varieduntil a standard readingis obt-ained on the, scales 33 or 55respectively and then a comparison of the weights required on any twowheels indicates their relative grades.

By the constructions described in connection with the two illustratedembodiments of k the invention, mechanism has been provided for? gradingabraslve wheelsand similar objects by a method including the steps ofholding a wearable tool in engagement with the body, giving them arelative motion so that an extended straight or curved path .will begenerated by any point in the active face of the tool and thenmeasuringthe drag or friction between the ,tool and the body and the amount wornfrom the tool. Both of these measurements are closely related to thegrinding ability of the wheel and by the use of these characteristicsthe action of the wheel may be predetermined with much greater degree ofaccuracy than has heretofore been possible. It will of course beunderstood that the measurement of force may be made in accordance withany suitable standard scale or an arbitrary one which has notsignificance in engineering practice since the, apparatus may be usedfor.

comparative as well as absolute measurements; hence the claims are to beinterpreted in this light.

What, I claim as new and desire to secure by Letters Patent is V '1: Themethod of grading an abrasive wheel comprising the steps of rotating thewheel at a fixed rate, causing a tool to bear against the wheel under adefinite pressure and move along an extended path thereon and measuringa force which varies with and is produced by the friction between thewheel and the tool during such movement.

2. The method of grading an abrasive i wheel comprising the steps ofrotating the wheel at a predetermined speed, causing a tool to engagethe wheel and thereby generate. a circular path on the wheel,maintaining. a standard pressure between the tool and the wheel andmeasuring the force re ired to overcome frictioir between the tool andthe wheel.

3. The'method of grading an abrasive wheel comprising the steps ofrotating'the wheel at a predetermined speed, causing a tool of standarddimensions and material to beanagainst the wheel in an extended path,maintaining a co stant pressure therebe-: tween, determining thefrictional and abrasive resistance between the wheel and the tool andcomparing the data thus obtained with measurements similarly made uponstandard wheels. 'f 1 4. The method of grading an abrasive wheelcomprising the steps of cans? a wearable tool to bear against the wheel,relatively moving the wheel and the tool so that the tool will describeon the wheelan extended path, measuring the force of the frictional dragbetween the wheel and the tooland measuring the wear on the tool.; 5. Amachine for abrasive wheels drag between the relatively moving wheel andtool.

6. A machine for grading abrasive wheels comprising means for rotatablysupporting the wheel to be graded, a tool adapted to engage the wheel ina circular-path during said rotation, means to produce sure between thetool to resist movement of the tool under the frictional pressure of therotating wheel and means to indicate the force necessary to resist suchmovement.

7. A machine for grading abrasive wheels comprising a rotatably mountedwheel supwheel and means port, a pivotally mounted arm carrying a tooladapted to frictionally engage a wheel on said support, a spring tocontrol the position of the arm, means for adjusting the spring toposition for measuring the force a definite pres-. and the wheel,'meansthe arm on a radius of the required by the rotating 'wheeL.

8. A machine for gradingabrasive wheels comprising a rotatably mountedwheel support, a pivotally mounted arm carrying a wearable todl bearingon a wheel on said support, means for measuring the friction between thetool and the wheel, means for moving the arm into a second position andmeans for measuring the tool" in the second mg on a wheel on saidsupport, a spring to control the position of the arm in one plane,

means to indicate'the force exerted'on the spring by friction. of therotating wheel on the tool and means for measuring the Wear on the toolwhen it is swung in the second plane. V Signed at Worcester, 20th day ofOct, 1919.

orLARn s is. GILLETT.

Massachusetts, this to hold the arm in such position I under thefrictional drag exerted on the tool

